JPH02308259A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To obtain the electrophotographic sensitive body which is free from the deterioration in characteristics even after repetitive use by using a hydrazone deriv. having a specific structure as a charge transfer material thereby obtaining a high sensitivity and low residual potential. CONSTITUTION:The hydrazone deriv. expressed by constitutional formula (1) is incorporated as the charge transfer material into the charge transfer layer to constitute the electrophotographic sensitive body. The charge transfer layer is obtd. by dissolving the above-mentioned hydrazone deriv. together with a binder resin into a solvent, applying the solvent on a charge generating layer and drying the coating. A hole transferable charge transfer material, such as pyrazoline deriv., may be added in addition to the above-mentioned hydrazone deriv. into the charge transfer layer. The mixing ratio of the other charge transfer with respect to the hydrazone deriv. is preferably in a (100:1) to (100:500) range.

Description

[Detailed Description of the Invention] [Summary] The purpose of the present invention is to obtain an organic photoreceptor used in electrophotography that has high sensitivity, low residual potential, and exhibits little property deterioration even after repeated use. In a laminated photoreceptor having at least a charge generation layer and a charge transport layer on a support, the charge transport layer contains a small amount of a hydrazone derivative (both represented by the following structural formula (1)) as a charge transport substance, and the electrophotographic photoreceptor is make up the body.

Arz　　　　R.

Here, R and Li represent a lower alkyl group, R2 represents a hydrogen 1 lower alkyl group, and Ar I and Ar2 represent an aryl group which may be substituted with a lower alkyl group, a lower alkoxy group, or an alkyl-substituted amino group.

Further, Ar, , Ar, may jointly form a heterocycle.

[Industrial application field]

The present invention relates to an electrophotographic photoreceptor using a hydrazone derivative as a charge transport material.

Electrophotographic technology is widely used in copying machines, but it is also used in information devices such as printers and facsimiles.

The electrophotographic process consists of charging, exposure, development, transfer, and fixing steps, and printed matter can be obtained by repeating these steps.

In this charging, a uniform positive or negative electrostatic charge is applied to the surface of the photoreceptor having photoconductivity.

In the subsequent exposure process, an electrostatic latent image corresponding to the image information is formed on the photoreceptor by irradiating it with laser light or the like to erase the surface charge on a specific portion.

This latent image is then electrostatically developed with toner or powder ink to form a visible image on the photoreceptor.

Finally, a desired printed matter can be obtained by electrostatically transferring this toner image onto recording paper and fusing it with heat, light, pressure, or the like.

In such electrophotographic processes, organic photoreceptors having photoconductivity have come to be used in place of conventional inorganic photoreceptors.

[Conventional technology]

Inorganic photoreceptors typified by selenium (Se)-based photoreceptors are widely used as photoreceptors having photoconductivity.

This m-less photoreceptor has high sensitivity and excellent abrasion resistance, and can be passed through high-speed, large-sized machines, but on the other hand, the photoreceptor layer must be made using a vacuum evaporation method, and Se does not harm the human body. Because it is harmful, it must be recovered, and for this reason, the cost is high, making it difficult to apply it to small, low-cost machines that do not require maintenance.

Organic photoreceptors were developed as an alternative to inorganic photoreceptors, and because they can be manufactured by a coating method, it has become easier to reduce costs through mass production.

Furthermore, compared to inorganic photoreceptors using Se or the like, organic photoreceptors have a wider range of materials to choose from, can select non-toxic compounds, and can be disposed of by users.

Next, although the photosensitive performance of organic photoreceptors is generally inferior to that of non-mold photoreceptors, the development of functionally separated photoreceptors that separate charge generation and transport has significantly improved sensitivity. It has become possible.

FIG. 1 shows the structure of a functionally separated laminated photoreceptor, in which a charge generation layer 2 and a charge transport layer 3 are laminated on a conductive support 1 made of aluminum (A metal, etc.) to form a photoreceptor 4.
is configured.

In 2\, the charge generation layer 2 has the function of absorbing incident light and generating pairs (carrier pairs) in direct ratio with electrons, and the charge transport layer 3 retains charges on its surface, and the charge generation layer 2 It has the function of transporting one of the generated carriers to the surface of the charge transport layer 3 to form an electrostatic latent image.

The charge generation layer 2 is formed by depositing a charge generation substance that absorbs light and generating carrier bare, or by dispersing it in a binder resin. Azo pigments and the like are known, and polyester, polyvinyl butyral, etc. are used as the binder resin.

The charge transport layer 3 is formed by dissolving a charge transport material having carrier transport ability into a binder resin.

Charge transport materials include electron transport charge transport materials such as trinitrofluorenone, which have the property of transporting electrons, and charge transport materials such as hydrazone and pyrazoline, which have the property of transporting holes. Examples of materials used include polycarbonate and polystyrene-acrylic.

By separating the functions of the photoreceptor into two layers in this way, it is possible to select the optimal compound for each function almost independently, resulting in sensitivity and two spectral characteristics.

Various properties such as charge retention, high-speed response, and mechanical wear resistance were dramatically improved.

However, the sensitivity of organic photoreceptors is still lower than that of inorganic photoreceptors such as Se, and there is a problem in that the charge transport material deteriorates due to repeated charging and exposure.

[Problem to be solved by the invention]

As described above, the sensitivity of organic photoreceptors is still lower than that of inorganic photoreceptors such as Se, and it is still difficult to apply them to high-speed printers.

In addition, as the charging and exposure processes are repeated, the charge transport material is partially decomposed by the ozone (0,) generated during charging and the irradiation light, which causes a decrease in the charging potential and an increase in the residual potential. , the problem is that the print quality deteriorates.

(Means for solving the problem) The above problem is solved by using a multilayer photoreceptor having a charge ordering layer and a charge transport layer on a conductive support, in which a charge transport substance having at least the following structural formula is used in the charge transport layer. This problem can be solved by constructing an electrophotographic photoreceptor containing the hydrazone derivative shown in (1).

Here, R9 represents a lower alkyl group, R2 represents hydrogen or a lower alkyl group, and Ar++Ar2 represents an aryl group optionally substituted with a lower alkyl group, a lower alkoxy group, or an alkyl-substituted amino group.

Moreover, Ar+ and Arz may jointly form a heterocycle.

[Effect]

As mentioned above, the charge transport layer is formed by dissolving a charge transport material having carrier transport ability into a binder resin, and the charge transport material includes an electron transport charge transport material such as trinitrofluorenone or chloranil. There are hole-transporting and charge-transporting substances such as hydrazone and birapurin, but the latter is more widely available and is generally used.

As mentioned above, hydracine is a hole-transporting substance and is a well-known material, but the inventors reexamined this material and found that the hydrazone derivative having the structure of formula (1) is as follows. It has been discovered that the photoreceptor has significantly superior properties as compared to the known hydrazone derivative represented by formula (2).

That is, the inventors selected the following two points as necessary conditions for an organic compound having hole conductivity, and selected a material that satisfies these conditions.

■ Having a long conjugated system; ■ Containing an electron-donating group. In this case, ■ is because electron conduction is facilitated by overlapping electron clouds of π electrons, and ■ is due to ionization due to the introduction of an electron-donating group. This is because it is known that the potential decreases, making it easier for holes to be injected from the charge generation layer.

As a result, it has been found that the hydrazone derivative represented by the structural formula (1) has much better properties than the hydrazone derivative represented by the structural formula (2).

The charge transport layer can be obtained by dissolving the above-mentioned hydrazone derivative together with a binder resin in a solvent, coating the solution on the charge generation layer, and drying the solution.

Here, the hydrazone derivative represented by the structural formula (1) can be easily synthesized from the hydrazine represented by (3) 2 and the ketone or aldehyde represented by the formula (4) by a known method.

Arz Here, R8 represents a lower alkyl group, R2 represents hydrogen or a lower alkyl group, and Ar represents an aryl group optionally substituted with a lower alkyl group, a lower alkoxy group, or an alkyl-substituted amino group. .

Furthermore, A r 1 + A r 2 may jointly form a heterocycle.

In addition, the binder resin is polycarbonate polystyrene,
Polyacrylonitrile, polyacrylic/styrene, polyester, polysulfone, etc. can be used.

The solvent is selected depending on the benzothiazole derivative and binder resin used, but examples include tetrahydrofuran, dioxane, chloroform, dichloromethane, dichloroethane,
Various organic solvents such as toluene and xylene can be used alone or in combination. Application methods include dip coat, spray coat, wire bar code, and doctor blade coat.

The appropriate film thickness is 5 to 50 μm, especially 10 μm.
It is desirable to set it to 30 micrometers.

Further, in addition to the above-mentioned hydrazone derivative, a hole-transporting charge transport substance such as a pyrazoline derivative may be added to the charge transport layer.

In this case, the mixing ratio of the other charge transporting substance to the hydrazone derivative is preferably in the range of 100:1 to 100:500.

Next, various metal phthalocyanines and azo pigments such as metal-free phthalocyanine, copper phthalocyanine, aluminum chloride phthalocyanine, titanyl phthalocyanine, and vanadyl phthalocyanine can be used as the charge generating substance.

The charge generating layer can be formed by depositing these charge generating substances on a conductive support, or by coating a mixture dispersed with a binder resin and drying it.

The binder resin for the charge generation layer is selected from polyester, polyvinyl alcohol, polyvinyl butyral, polyamide, etc., taking into consideration the adhesion to the base and the dispersibility of the charge generation substance.

The solvent is selected depending on the charge generating substance and binder resin used, and various organic solvents such as tetrahydrofuran, dioxane, methanol, ethanol, dichloromethane, toluene, and kyrylene can be used alone or in combination.

The coating method on the support can be the same as in the case of the charge transport layer.

A suitable film thickness is 0.01 to 3 μm, and a thickness of 1 μm or less is particularly desirable.

Further, the stacking order of the charge generation layer and the charge transport layer may be reversed.

As the conductive support, for example, aluminum is used.

Examples include resins that have been made conductive by adding metals such as copper, tin oxide, carbon, and the like.

It also improves the adhesion between the support and the photosensitive layer.

An undercoat layer can be provided to prevent thermal carrier injection.

As this undercoat layer, resins such as polyvinyl alcohol, polyvinyl butyral, polyamide, and epoxy, or resins containing additives such as tin oxide, indium oxide, and titanium oxide are used.

〔Example〕

Specifically, the hydrazone derivative represented by the structural formula (1) can be represented as various compounds as shown in Nos. 011 to 8 in FIG.

An example of the synthesis of the hydrazone derivative of N011 is as follows.

2.207 g of 1,1-diphenylhydrazone hydrochloride (
0.01 mol), 2-acetylthiophene 1.262
g (0.01 mol) dissolved in 40 ml of methanol,
The mixture was heated to reflux for 5 hours while stirring.

After cooling, add a large amount of pure water and collect the resulting precipitate by filtration.
Recrystallization was performed twice using methanol, and then recrystallization was performed using a mixed solvent of hexane and ethyl acetate to obtain 2.122 g of pale yellow needle-like crystals in a yield of 72.6%.

The melting point of this crystal is 134-136°C, and as a result of elemental analysis, the calculated and measured values almost match as shown in Table 1, confirming that it is a No. 1 hydrazone derivative. was completed.

Compounds No. 2 to 8 in Table 1 were similarly synthesized from the corresponding hydrazine and ketone, and subjected to elemental analysis.

Examples in which hydrazone derivatives Nos. 1 to 8 are used as charge transport materials will be described below.

Example 1: 1 part by weight of titanium oxide phthalocyanine, 1 part by weight of polyester, 9 parts by weight of dichloromethane, and 9 parts by weight of dichloroethane were mixed using hard glass beads and a hard glass pot.
The time-dispersed mixture was applied onto the aluminum surface of an aluminum vapor-deposited polyester film using a doctor blade method.
It was dried at °C for 1 hour to form a charge generation layer with a thickness of about 0.3 μm.

Next, 1 part by weight of the hydrazone derivative shown in No. 1 in FIG. The photoreceptor was dried for 2 hours at C for 2 hours to form a charge transport layer with a thickness of 20 μm, thereby obtaining a photoreceptor as shown in FIG.

This photoreceptor was subjected to corona discharge at -5 and ■, and the surface potential after 1 second was ν. 780 nm from that moment as (V),
Exposure was carried out at l u14/cm2.

And the surface potential is V. The time it takes to reach half of t1/
2, and the half-reduced exposure amount E I/□ (μJ/cm2) was calculated.

Furthermore, the surface potential νr (
V) is recorded, and finally the static electricity is removed using a 630 nm LED.
Finished the process. , and this process was repeated 5000 times, and the results are shown in Table 2.

Examples 2 to 4 In Example 2, N in Figure 2 was used as a hydrazone derivative.
No. 3 in Example 3.

A photoreceptor was prepared in the same manner as in Example 1 except that compound No. 6 was used in Example 4, and compound No. 7 was used.
Its performance is shown in Table 2.

Comparative Example 1 The same method as in Example 1 was carried out, except that ordinary hydrazine shown by Structural Formula (2) was used instead of the hydrazone derivative shown by Structural Formula (1) as a charge transport material, and the results were as follows. It is shown in Table 2 on page 2.

As can be seen from this table, the photoreceptor according to the present invention shows almost no deterioration in characteristics even after repeated testing 5000 times.

On the other hand, although the photoreceptor of the comparative example showed relatively good characteristics in the initial stage, after continuous testing, the sensitivity decreased, the residual potential increased, etc., and the photoreceptor deteriorated. I can see that you are doing it.

Table 2 [Effects of the Invention] As described above, by using the hydrazone derivative represented by the structural formula (1) as a charge transport material, high sensitivity and low residual potential can be obtained, and even after repeated use. An electrophotographic photoreceptor without deterioration of characteristics can be obtained.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a functionally separated laminated photoreceptor, and FIG. 2 is a hydradun conductor according to an embodiment. In the figure, 1 is a conductive support, 2 is a charge generation layer, 3 is a charge transport layer, and 4 is a photoreceptor. Figure 1 No, I No, 2 No, 3 No, 4 After the odor comes No, 6 No, 7 N□, δ ゛Hydrazoone derivative 2 figure

Claims (1)

[Scope of Claims] A laminated photoreceptor having at least a charge generation layer and a charge transport layer on a conductive support, at least a hydrazone derivative represented by the following structural formula (1) as a charge transport substance in the charge transport layer. An electrophotographic photoreceptor characterized by containing. ▲There are mathematical formulas, chemical formulas, tables, etc.▼...(1) Here, R_1 is a lower alkyl group, R_2 is hydrogen or a lower alkyl group, and Ar_1 and Ar_2 are a lower alkyl group, a lower alkoxy group, or an alkyl group. Represents an aryl group which may be substituted with a substituted amino group. Further, Ar_1 and Ar_2 may jointly form a heterocycle.